我正在遍历一个dynamodb表并建立一个包含所有表行的csv文件。但是，csv中的大多数条目都是重复的。dynamodb表中大约有350k条唯一记录（所有记录都是唯一的）。生成的文件（使用下面的代码）只有大约4k个唯一的条目，其余的都是重复的。

public void fetchItems() throws IOException {
    AmazonDynamoDB amazonDynamoDB = DynamoDBClient.getInstance().getConnection();
    ScanResult result = null;
    ScanRequest req = new ScanRequest().withTableName("TABLE_NAME");
    List<Map<String, AttributeValue>> records = new ArrayList<Map<String, AttributeValue>>();
    do {
        if (result != null) {
            req.setExclusiveStartKey(result.getLastEvaluatedKey());
        }
        result = amazonDynamoDB.scan(req);
        List<Map<String, AttributeValue>> rows = result.getItems();
        Map<String, AttributeValue> staticColumnRecord = new HashMap<String, AttributeValue>();
        for (Map<String, AttributeValue> map : rows) {
            List<String> snowFlakeColumnsListApparel = new ArrayList<String>(Arrays.asList(apparelColumns));
            for (String key : snowFlakeColumnsListApparel) {
                AttributeValue value = map.get(key);
                if (value != null) {
                    staticColumnRecord.put(key, value);
                } else {
                    staticColumnRecord.put(key, new AttributeValue().withS("null"));
                }
            }
            records.add(staticColumnRecord);
        }

    } while (result.getLastEvaluatedKey() != null);
    buildCSV(records);
}

private void buildCSV(List<Map<String, AttributeValue>> changedRecords) throws IOException {
    List<String> headers = changedRecords.stream().flatMap(map -> map.keySet().stream()).distinct()
            .collect(Collectors.toList());
    try (FileOutputStream fos = new FileOutputStream(file);
            OutputStreamWriter bwr = new OutputStreamWriter(fos, StandardCharsets.UTF_8)) {
        StringBuffer headerContent = new StringBuffer();
        for (String string : headers) {
            headerContent.append(string);
            headerContent.append(",");
        }
        StringBuffer strBuilder = new StringBuffer();
        for (Map<String, AttributeValue> lmap : changedRecords) {
            StringBuilder stringBuilder = new StringBuilder("");
            String sep = "";
            for (Entry<String, AttributeValue> string2 : lmap.entrySet()) {
                String value = string2.getValue().getS();
                stringBuilder.append(sep).append("\"").append(value).append("\"");
                sep = ",";
            }
            if (!stringBuilder.toString().isEmpty()) {
                strBuilder.append(stringBuilder).append(System.getProperty("line.separator"));
            }
        }
        headerContent.append("\n");
        headerContent.append(strBuilder);
        bwr.write(headerContent.toString());

    } catch (IOException e) {
        e.printStackTrace();
    }
}